The universal mobile telecommunication system (UMTS) is a European-type, third generation IMT-2000 mobile communication system that has evolved from a European standard known as Global System for Mobile communications (GSM). UMTS is intended to provide an improved mobile communication service based upon a GSM core network and wideband code division multiple access (W-CDMA) wireless connection technology. In December 1998, a Third Generation Partnership Project (3GPP) was formed by the ETSI of Europe, the ARIB/TTC of Japan, the T1 of the United States, and the TTA of Korea. The 3GPP creates detailed specifications of UMTS technology. In order to achieve rapid and efficient technical development of the UMTS, five technical specification groups (TSG) have been created within the 3GPP for standardizing the UMTS by considering the independent nature of the network elements and their operations. Each TSG develops, approves, and manages the standard specification within a related region. Among these groups, the radio access network (RAN) group (TSG-RAN) develops the standards for the functions, requirements, and interface of the UMTS terrestrial radio access network (UTRAN), which is a new radio access network for supporting W-CDMA access technology in the UMTS.
FIG. 1 shows an overview of the UMTS network 100, including the terminal or user equipment (UE) 110, the UTRAN 120 and the core network (CN) 130.
The UTRAN 120 is composed of several Radio Network Controllers (RNCs) 124, 126 and Node Bs 122, which are connected via the lub interface. Each RNC may control several Node Bs. Each Node B may control one or several cells, where a cell is characterised by the fact that it covers a given geographical area on a given frequency. Each RNC is connected via the lu interface to the CN, i.e. towards the MSC (Mobile-services Switching Center) entity 132 of the CN and the SGSN (Serving GPRS Support Node) entity 131. The RNCs can be connected to other RNCs via the lur interface. The RNC handles the assignment and management of radio resources and operates as an access point with respect to the core network.
The Node Bs receive information sent by the physical layer of the terminal (UE) through an uplink and transmit data to the terminal through a downlink. The Node Bs operate as access points of the UTRAN for the terminal. The SGSN is connected via the Gf interface to the EIR (Equipment Identity Register) 133, via the Gs interface to the MSC 132, via the Gn interface to the GGSN (Gateway GPRS Support Node) 135 and via the Gr interface to the HSS (Home Subscriber Server) 134. The EIR hosts lists of terminals (UEs) which are allowed or are not allowed to be used on the network. The MSC 132 which controls the connection for CS (circuit switched) services is connected via the NB interface towards the MGW (Media Gateway) 1361 via the F interface towards the EIR 133, and via the D interface towards the HSS 134. The MGW 136 is connected via the C interface towards the HSS 134, and to the PSTN (Public Switched Telephone Network), and allows adapting of the codecs between the PSTN and the connected RAN.
The GGSN 135 is connected via the Gc interface to the HSS 134, and via the Gi interface to the Internet. The GGSN 135 is responsible for routing, charging and separation of data flows into different RABs (Radio Access Bearers). The HSS 134 handles the subscription data of the users.
Other existing connections will not be described in detail, but would be understood by those skilled in the art.
The UTRAN 120 constructs and maintains a radio access bearer (RAB) for communication between the terminal (UE) 110 and the core network (CN) 130. The core network requests end-to-end quality of service (QoS) requirements from the RAB, and the RAB supports the QoS requirements the core network has set. Accordingly, by constructing and maintaining the RAB, the UTRAN can satisfy the end-to-end QoS requirements.
The services provided to a specific terminal (UE) are roughly divided into circuit switched (CS) services and packet switched (PS) services. For example, a general voice conversation service is a circuit switched service, while a Web browsing service via an Internet connection is classified as a packet switched (PS) service.
For supporting circuit switched services, the RNCs 124, 126 are connected to the mobile switching center (MSC) 132 of the core network and the MSC 132 is connected to the gateway mobile switching center (GMSC) that manages the connection with other networks. For supporting packet switched services, the RNCs are connected to the Serving GPRS (General Packet Radio Service) Support Node (SGSN) 131 and the Gateway GPRS Support Node (GGSN) 135 of the core network. The SGSN 131 supports the packet communications with the RNCs and the GGSN 135 manages the connection with other packet switched networks, such as the Internet.
FIG. 2 illustrates a structure of a radio interface protocol between the terminal (UE) and the UTRAN according to the 3GPP radio access network standards. As shown in FIG. 2, the radio interface protocol has horizontal layers comprising a physical layer, a data link layer, and a network layer, and has vertical planes comprising a user plane (U-plane) for transmitting user data and a control plane (C-plane) for transmitting control information. The user plane is a region that handles traffic information with the user, such as voice or Internet protocol (IP) packets. The control plane is a region that handles control information for an interface with a network, maintenance and management of a call, and the like.
The protocol layers in FIG. 2 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the three lower layers of an open system interconnection (OSI) standard model. The first layer (L1), namely, the physical layer, provides an information transfer service to an upper layer by using various radio transmission techniques. The physical layer is connected to an upper layer called a medium access control (MAC) layer, via a transport channel. The MAC layer and the physical layer exchange data via the transport channel. The second layer (L2) includes a MAC layer, a radio link control (RLC) layer, a broadcast/multicast control (BMC) layer, and a packet data convergence protocol (PDCP) layer. The MAC layer handles mapping between logical channels and transport channels and provides allocation of the MAC parameters for allocation and re-allocation of radio resources. The MAC layer is connected to an upper layer called the radio link control (RLC) layer, via a logical channel. Various logical channels are provided according to the type of information transmitted. In general, a control channel is used to transmit information of the control plane and a traffic channel is used to transmit information of the user plane. A logical channel may be a common channel or a dedicated channel depending on whether the logical channel is shared. Logical channels include a dedicated traffic channel (DTCH), a dedicated control channel (DCCH), a common traffic channel (CTCH), a common control channel (CCCH), a broadcast control channel (BCCH), and a paging control channel (PCCH), or a Shared Control Channel (SCCH) and other channels. The BCCH provides information including information utilized by a terminal to access a system. The PCCH is used by the UTRAN to access a terminal.
To support point-to-multipoint services, such as multimedia broadcast/multicast services (MBMS or MBMS services), additional traffic and control channels are introduced in the MBMS standard. For example, the MCCH (MBMS point-to-multipoint Control Channel) is used for transmission of MBMS control information, the MTCH (MBMS point-to-multipoint Traffic Channel) is used for transmitting MBMS service data, and the MSCH (MBMS Scheduling Channel) is used to transmit scheduling information.
The different types of logical channels that exist can be depicted as follows:

The MAC layer is connected to the physical layer by transport channels and can be divided into a MAC-b sub-layer, a MAC-d sub-layer, a MAC-c/sh sub-layer, a MAC-hs sub-layer and a MAC-m sublayer according to the type of transport channel being managed. The MAC-b sub-layer manages a BCH (Broadcast Channel), which is a transport channel handling the broadcasting of system information. The MAC-cish sub-layer manages a common transport channel, such as a forward access channel (FACH) or a downlink shared channel (DSCH), which is shared by a plurality of terminals, or in the uplink the Random Access Channel (RACH). The MAC-m sublayer may handle the MBMS data.
FIG. 3 shows the possible mapping between the logical channels and the transport channels from the UE perspective.
FIG. 4 shows the possible mapping between the logical channels and the transport channels from the UTRAN perspective.
The MAC-d sub-layer manages a dedicated channel (DCH), which is a dedicated transport channel for a specific terminal. The MAC-d sublayer is located in a serving RNC (SRNC) that manages a corresponding terminal, and one MAC-d sublayer also exists in each terminal. The RLC layer, depending of the RLC mode of operation, supports reliable data transmissions and performs segmentation and concatenation on a plurality of RLC service data units (SDUs) delivered from an upper layer. When the RLC layer receives the RLC SDUs from the upper layer, the RLC layer adjusts the size of each RLC SDU in an appropriate manner based upon processing capacity, and then creates data units by adding header information thereto. These data units, called protocol data units (PDUs), are transferred to the MAC layer via a logical channel. The RLC layer includes a RLC buffer for storing the RLC SDUs and/or the RLC PDUs.
The BMC layer schedules a cell broadcast (CB) message transferred from the core network and broadcasts the CB message to terminals positioned in a specific cell or cells.
The PDCP layer is located above the RLC layer. The PDCP layer is used to transmit network protocol data, such as IPv4 or IPv6, efficiently on a radio interface with a relatively small bandwidth. For this purpose, the PDCP layer reduces unnecessary control information used in a wired network, namely, a function called header compression is performed.
The radio resource control (RRC) layer located at the lowest portion of the third layer (L3) is only defined in the control plane. The RRC layer controls the transport channels and the physical channels in relation to setup, reconfiguration, and the release or cancellation of the radio bearers (RBs). The RB signifies a service provided by the second layer (L2) for data transmission between the terminal and the UTRAN. In general, the set up of the RB refers to the process of stipulating the characteristics of a protocol layer and a channel required for providing a specific data service, and setting the respective detailed parameters and operation methods. Additionally, the RRC layer handles user mobility within the RAN, and additional services, e.g., location services.
FIG. 5 shows a UE with channels (DCH, HS-DSCH) established with multiple cells managed by Node Bs, which are controlled by an RNC in a network.
The different possibilities that exist for the mapping between the radio bearers and the transport channels for a given UE are not all possible all the time. The UE/UTRAN can deduce the possible mapping depending on the UE state and the procedure that the UE/UTRAN is executing. The different states and modes are explained in more detail below, as far as they concern the present invention.
The different transport channels are mapped onto different physical channels. The configuration of the physical channels is given by RRC signalling exchanged between the RNC and the UE.
The RRC mode refers to whether there exists a logical connection between the RRC of the terminal and the RRC of the UTRAN. If there is a connection, the terminal is said to be in RRC connected mode. If there is no connection, the terminal is said to be in idle mode. Because an RRC connection exists for terminals in RRC connected mode, the UTRAN can determine the existence of a particular terminal within the unit of cells, for example which cell or set of cells the RRC connected mode terminal is in, and which physical channel the UE is listening to. Thus, the terminal can be effectively controlled.
In contrast, the UTRAN cannot determine the existence of a terminal in idle mode. The existence of idle mode terminals can only be determined by the core network to be within a region that is larger than a cell, for example a location or a routing area. Therefore, the existence of idle mode terminals is determined within large regions, and in order to receive mobile communication services such as voice or data, the idle mode terminal must move or change into the RRC connected mode.
FIG. 6 shows the possible transitions between modes and states of a UE. A UE in RRC connected mode can be in different states, e.g. CELL_FACH state, CELL_PCH state, CELL_DCH state or URA_PCH state. Other states could exist as well. Depending on these states, the UE carries out different actions and listens to different channels. For example, a UE in CELL_DCH state will try to listen to DCH type transport channels (amongst other channels), which may comprise DTCH and DCCH transport channels, and which can be mapped to a certain DPCH, DPDSCH, or other physical channels. The UE in CELL_FACH state will listen to several FACH transport channels, which are mapped to a certain S-CCPCH. The UE in PCH state will listen to the PICH channel, and to the PCH channel that is mapped to a certain S-CCPCH physical channel.
The network (UTRAN) may provide various types of services to a terminal (UE). One example would be multimedia broadcast/multicast service, also referred to as MBMS or MBMS service.
At the start of a service, the UE is supposed to read different messages depending on the situation. For example, the UE should acquire counting, establish RRC connections, receive a MTCH, and the like.
In order to send and receive these messages, a particular order (sequence or arrangement) is used such that messages for which the content has changed is sent/received before messages for which the content has not changed.
MBMS signalling on the MCCH makes use of identifiers to allow reference information to be carried in one message (message A) and which is referred to in another message (message B). These identifiers are valid only for messages that have been read in the same modification period.
In the related art, the messages are ordered merely based upon whether or not their content has changed. Namely, messages containing changed contents are transmitted before messages containing no changed contents. However, this simple condition may not always be optimal.